1.
Менеджер вікон
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A window manager is system software that controls the placement and appearance of windows within a windowing system in a graphical user interface. Most window managers are designed to provide a desktop environment. Few window managers are designed with a distinction between the windowing system and the window manager. Every graphical user interface based on a windows metaphor has some form of window management, in practice, the elements of this functionality vary greatly. Elements usually associated with window managers allow the user to open, close, minimize, maximize, move, resize, many window managers also come with various utilities and features, e. g. docks, task bars, program launchers, desktop icons, and wallpaper. On systems using the X window system, there is a distinction between the window manager and the windowing system. Strictly speaking, an X window manager does not directly interact with hardware, mice. Users of the X Window System have the ability to use many different window managers – Metacity, used in GNOME2, and KWin, used in KDE Plasma Workspaces. Since many window managers are modular, people can use others, such as Compiz, sawfish and awesome on the other hand are extensible window managers offering exacting window control. Components of different window managers can even be mixed and matched, for example, Window managers under the X window system adopt applications from the root window and re-parent them to window decorations. Re-parenting can also be used to add the contents of one window to another, for example, a flash player application can be re-parented to a browser window, and can appear to the user as supposedly being part of that program. Re-parenting window managers can therefore arrange one or more programs into the same window, Microsoft Windows has provided an integrated stacking window manager since Windows 2.0, Windows Vista introduced the compositing Desktop Window Manager as an optional hardware-accelerated alternative. Since Windows 8, the Desktop Window Manager can no longer be disabled, the Windows window manager can also act as an X window manager through Cygwin/X in multiwindow mode. Note that Microsoft and X Window System use different terms to describe similar concepts, for example, there is no specific word for window manager functionality in Windows. Window managers are often divided into three or more classes, which describe how windows are drawn and updated, Compositing window managers let all windows be created and drawn separately and then put together and displayed in various 2D and 3D environments. The most advanced compositing window managers allow for a deal of variety in interface look and feel. All window managers that have overlapping windows and are not compositing window managers are stacking window managers, stacking window managers allow windows to overlap by drawing background windows first, which is referred to as painters algorithm. Changes sometimes require that all windows be re-stacked or repainted, which usually involves redrawing every window, tiling window managers paint all windows on-screen by placing them side by side or above and below each other, so that no window ever covers another

2.
Операційна система
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An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is Microsoft Windows with a market share of around 83. 3%. MacOS by Apple Inc. is in place, and the varieties of Linux is in third position. Linux distributions are dominant in the server and supercomputing sectors, other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can run one program at a time. Multi-tasking may be characterized in preemptive and co-operative types, in preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e. g. Solaris, Linux, cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking, 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem, a distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing, distributed computations are carried out on more than one machine. When computers in a work in cooperation, they form a distributed system. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses, embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy and they are able to operate with a limited number of resources. They are very compact and extremely efficient by design, Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is a system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could run different programs in succession to speed up processing

3.
Linux
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Linux is a Unix-like computer operating system assembled under the model of free and open-source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released on September 17,1991 by Linus Torvalds, the Free Software Foundation uses the name GNU/Linux to describe the operating system, which has led to some controversy. Linux was originally developed for computers based on the Intel x86 architecture. Because of the dominance of Android on smartphones, Linux has the largest installed base of all operating systems. Linux is also the operating system on servers and other big iron systems such as mainframe computers. It is used by around 2. 3% of desktop computers, the Chromebook, which runs on Chrome OS, dominates the US K–12 education market and represents nearly 20% of the sub-$300 notebook sales in the US. Linux also runs on embedded systems – devices whose operating system is built into the firmware and is highly tailored to the system. This includes TiVo and similar DVR devices, network routers, facility automation controls, televisions, many smartphones and tablet computers run Android and other Linux derivatives. The development of Linux is one of the most prominent examples of free, the underlying source code may be used, modified and distributed‍—‌commercially or non-commercially‍—‌by anyone under the terms of its respective licenses, such as the GNU General Public License. Typically, Linux is packaged in a known as a Linux distribution for both desktop and server use. Distributions intended to run on servers may omit all graphical environments from the standard install, because Linux is freely redistributable, anyone may create a distribution for any intended use. The Unix operating system was conceived and implemented in 1969 at AT&Ts Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, first released in 1971, Unix was written entirely in assembly language, as was common practice at the time. Later, in a key pioneering approach in 1973, it was rewritten in the C programming language by Dennis Ritchie, the availability of a high-level language implementation of Unix made its porting to different computer platforms easier. Due to an earlier antitrust case forbidding it from entering the computer business, as a result, Unix grew quickly and became widely adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs, freed of the legal obligation requiring free licensing, the GNU Project, started in 1983 by Richard Stallman, has the goal of creating a complete Unix-compatible software system composed entirely of free software. Later, in 1985, Stallman started the Free Software Foundation, by the early 1990s, many of the programs required in an operating system were completed, although low-level elements such as device drivers, daemons, and the kernel were stalled and incomplete. Linus Torvalds has stated that if the GNU kernel had been available at the time, although not released until 1992 due to legal complications, development of 386BSD, from which NetBSD, OpenBSD and FreeBSD descended, predated that of Linux. Torvalds has also stated that if 386BSD had been available at the time, although the complete source code of MINIX was freely available, the licensing terms prevented it from being free software until the licensing changed in April 2000

4.
Berkeley Software Distribution
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Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995. Today the term BSD is often used non-specifically to refer to any of the BSD descendants which together form a branch of the family of Unix-like operating systems, operating systems derived from the original BSD code remain actively developed and widely used. Historically, BSD has been considered a branch of Unix, Berkeley Unix, because it shared the initial codebase, in the 1980s, BSD was widely adopted by vendors of workstation-class systems in the form of proprietary Unix variants such as DEC ULTRIX and Sun Microsystems SunOS. This can be attributed to the ease with which it could be licensed, FreeBSD, OpenBSD, NetBSD, Darwin, and PC-BSD. The earliest distributions of Unix from Bell Labs in the 1970s included the source code to the system, allowing researchers at universities to modify. A larger PDP-11/70 was installed at Berkeley the following year, using money from the Ingres database project, also in 1975, Ken Thompson took a sabbatical from Bell Labs and came to Berkeley as a visiting professor. He helped to install Version 6 Unix and started working on a Pascal implementation for the system, graduate students Chuck Haley and Bill Joy improved Thompsons Pascal and implemented an improved text editor, ex. Other universities became interested in the software at Berkeley, and so in 1977 Joy started compiling the first Berkeley Software Distribution, 1BSD was an add-on to Version 6 Unix rather than a complete operating system in its own right. Some thirty copies were sent out, some 75 copies of 2BSD were sent out by Bill Joy. 2. 9BSD from 1983 included code from 4. 1cBSD, the most recent release,2. 11BSD, was first issued in 1992. As of 2008, maintenance updates from volunteers are still continuing, a VAX computer was installed at Berkeley in 1978, but the port of Unix to the VAX architecture, UNIX/32V, did not take advantage of the VAXs virtual memory capabilities. 3BSD was also alternatively called Virtual VAX/UNIX or VMUNIX, and BSD kernel images were normally called /vmunix until 4. 4BSD, 4BSD offered a number of enhancements over 3BSD, notably job control in the previously released csh, delivermail, reliable signals, and the Curses programming library. In a 1985 review of BSD releases, John Quarterman et al, many installations inside the Bell System ran 4. 1BSD. 4. 1BSD was a response to criticisms of BSDs performance relative to the dominant VAX operating system, the 4. 1BSD kernel was systematically tuned up by Bill Joy until it could perform as well as VMS on several benchmarks. Back at Bell Labs,4. 1cBSD became the basis of the 8th Edition of Research Unix, to guide the design of 4. The committee met from April 1981 to June 1983, apart from the Fast File System, several features from outside contributors were accepted, including disk quotas and job control. Sun Microsystems provided testing on its Motorola 68000 machines prior to release, the official 4. 2BSD release came in August 1983. On a lighter note, it marked the debut of BSDs daemon mascot in a drawing by John Lasseter that appeared on the cover of the printed manuals distributed by USENIX

5.
GTK+
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GTK+ is a cross-platform widget toolkit for creating graphical user interfaces. It is licensed under the terms of the GNU Lesser General Public License and it is one of the most popular toolkits for the Wayland and X11 windowing systems, along with Qt. The GTK+ library contains a set of graphical elements, version 3.13.3 contains 203 active and 37 deprecated widgets. GTK+ is a widget toolkit written in the C programming language, it uses GObject. While GTK+ is primarily targeted at windowing systems based upon X11 and Wayland, it works on other platforms, including Microsoft Windows, there is also an HTML5 back-end called Broadway. GTK+ can be configured to change the look of the widgets drawn, several display engines exist which try to emulate the look of the native widgets on the platform in use. Starting with version 2.8, released in 2005, GTK+ began the transition to using Cairo to render the majority of its control elements. Since GTK+ version 3.0, all the rendering is done using Cairo, GDK acts as a wrapper around the low-level functions provided by the underlying windowing and graphics systems. GDK is found in the /gdk directory, GSK is the rendering and scene graph API for GTK+. GSK lies between the control elements and the rendering. GSK was finally merged into GTK+ version 3.90 released March 2017, GSK is found in the /gsk directory. GtkInspector has been introduced with version 3.14, gtkInspector can only be invoked after installing the development package libgtk-3-dev/gtk+-devel. There are several GUI designers for GTK+, the following projects are active as of July 2011, Glade, supports GtkBuilder, which is a GTK+ built-in GUI description format. Gazpacho, GUI builder for the GTK+ toolkit written in Python Crow Designer, relies on its own GuiXml format, Stetic, part of MonoDevelop, oriented towards Gtk#. GtkBuilder allows user interfaces to be designed without writing code, the interface is described in an Extensible Markup Language file, which is then loaded at runtime and the objects created automatically. The Glade Interface Designer allows creation of the interface in a WYSIWYG manner. The description of the interface is independent from the programming language being used. A library written in one programming language may be used in another language if bindings are written, Gtk# is a set of. NET bindings for the GTK+ GUI toolkit and assorted GNOME libraries

Free software or libre software is computer software distributed under terms that allow users to run the software for …

Example of a modern free software operating system running some representative applications. Shown are the Xfce desktop environment, the Firefox web browser, the Vim text editor, the GIMP image editor, and the VLC media player.

The GNU General Public License (GNU GPL or GPL) is a widely used free software license, which guarantees end users the …

Richard Stallman at the launch of the first draft of the GNU GPLv3 at MIT, Cambridge, Massachusetts, USA. To his right is Columbia Law Professor Eben Moglen, chairman of the Software Freedom Law Center.